(1) Field of the Invention
This invention relates to a method of manufacturing vacuum hermetic vessels in which vacuum is maintained.
(2) Description of the Related Art
Conventionally, fluorescent display panels are well-known including field emission cathodes referred to as flat cold cathodes as well as anodes coated with fluorescent substance each which collects electrons emitted from the field emission cathode.
In the fluorescent display panel, the cathode and the anode are positioned in parallel so as to leave a small space. To maintain the gap between the cathode and the anode in vacuum, the cathodes and the anodes are contained in a vacuum hermetic vessel.
FIG. 6(a) illustrates the configuration of a vacuum hermetic vessel. In the vacuum hermetic vessel 100 shown in FIG. 6(a), the first substrate 102 and the second substrate 103 are placed so as to confront each other with a small distance spaced. The first substrate 102 and the second substrate are sealed with a sealing compound (not shown). The first substrate 102 and the second substrate are formed of, for example, glass. A group of flat field emission cathodes are formed on the first substrate 102. Anodes coated with a fluorescent are formed on the second substrate 103. The first substrate 102 and the second substrate 103 are spaced 200 NM to 500 NM and hermetically sealed with a sealing compound.
The first substrate 102 and the second substrate 103 are placed in an elongate direction to confront each other at a position somewhat shifted. As shown in FIG. 6(a), the first substrate is larger than the second substrate 103 and its three sides protrude outward from the second substrate 103. A portion of the second substrate 103 protrudes from the remaining side of the first substrate 102. To cover the protruded portion of the second substrate 103, the rectangular getter box 104 internally containing a getter is sealed on the first substrate 102 using a sealing compound. A rectangular communication hole piece 109 with the communication hole 106 formed on the side surface thereof, shown in FIG. 6(b), is securely fixed between the protruded portion of the second substrate 103 and the getter box 104. The communication hole piece 109 is further sealed hermetically between the second substrate 103 and the getter box 104 using a sealing compound.
The communication hole 106 formed in the communication hole piece 109 communicates the space containing a display portions formed with the first substrate 102 and the second substrate 103, with the getter box 104.
An exhaust tube 105 is welded on the top surface of the getter box 104. A hole communicating the exhaust tube 105 with the getter box 104 is formed on the top surface of the getter box 104.
The getter box 104 contains a getter. The getter generally is an evaporation type getter including Ba--Al alloy contained in a ring metal member. While the ring member is externally heated by radio-frequency induction, the Ba--Al alloy is heated and evaporated onto the internal wall surface of the getter box 104, thus forming a getter mirror.
In the vacuum hermetic vessel manufacturing method, the first substrate (cathode substrate) 102 on which field emission cathodes are formed and the second substrate (anode substrate) 103 on which anodes coated with fluorescence are prepared. Then, the first substrate 102 is superposed on the second substrate 103. The getter box 104 is placed at a predetermined position. The first substrate 102 and the second substrate 103 are sealed together with the getter box 104. The space (gap) between the first substrate 102 and the substrate 103 is drawn to a vacuum by exhausting the air through the exhaust tube 105. Finally, after the exhaust tube 104 is sealed by welding and then cut, a vacuum hermetic vessel is completely produced.
As described above, according to the conventional vacuum hermetic vessel manufacturing method, after plural field emission cathodes are formed on a single substrate, the single substrate is separated into respective cathode substrates. Similarly, after plural anodes coated with fluorescence are formed on a single substrate, the signal substrate is separated into respective anode substrates. Then vacuum hermetic vessels are respectively fabricated through the above-mentioned manufacturing steps. Hence, the problem is that since plural vacuum hermetic vessels cannot be manufactured in a batch process, the conventional manufacturing method has its limit in the mass production.